1. Field of Invention
The present invention relates to a field effect transistor and a fabricating method thereof, and more particularly to a multi-fin field effect transistor and a fabricating method thereof.
2. Description of Related Art
With the device size gradually shrunken, in order to satisfy multiple applications of an integrated circuit in future, currently, the transistor shape of a semiconductor device is developed from a planar gate structure to a vertical gate structure.
Now, some patents have disclosed relevant technology focusing on this aspect. For example, US Patent No. 2004/0227181 has disclosed a multi-channel transistor and a fabricating method thereof. The aforementioned document is the reference of the present invention.
However, the conventional semiconductor device with a vertical gate structure still has some problems that are not solved. For example, the most serious problem of the conventional device is the floating body effect. The floating body effect refers to that, in a semiconductor device, charges may be accumulated in channels. Once the charges are accumulated in the channels to some extent, not only the threshold voltage of the semiconductor device is affected, but also the current in a drain region is suddenly increased. Furthermore, the floating body effect causes the semiconductor device turn on automatically without applying a voltage, thereby influencing reliability and stability of the semiconductor device and causing leakage current.
From the other aspect, the semiconductor device is mostly formed through an epitaxial process. However, the epitaxial process takes a long time and it is always difficult to clean the surface of an epitaxial layer. In addition, the epitaxial process cannot be readily controlled, resulting in facet effect and influencing the subsequent processes.